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Biological Perspective, Diagnostic Methods, Brain Structure, Principles -…

- - - - https://docs.google.com/document/d/1rsikl_PGsJWAme8kJmw_0slnOKo2tTiGuOhQgdSlyqo/edit
    - - Dendrites receive information
      - Soma integrates this info and sends a message through the axon to the axon terminal
      - Axon terminal sends the info to the next neuron via neuro-transmitters
  - - - When a memory is created and regularly revisited, new receptor sites are created AND the dendrites create more “antennas” to receive these messages (dendritic branching/growth)
      - More neuro-transmitters are released (so, more electro-chemical messages are sent), which enhances the efficiency of the retrieval of the memory
      - Long-term potentiation: long-lasting enhancing of this communication (synaptic transmission), which creates a very efficient neural trace. The more we revisit that memory, the easier it is to retrieve it (e.g. passwords)
- - - - loss of articulated speech
    - - impairment of language comprehension - speech production is intact
- - - - depending on ion channel opened, neuron becomes more or less excitable
  - - - released from the terminal buttons
      - fit into receptor sites on the post-synaptic membrane.
      - Neurotransmitters can either
        
        excite a neuron – excitatory neurotransmitters
        
        inhibit a neuron –inhibitory neurotransmitters
      - Excitatory NT increase the likelihood that the neuron will fire an action potential, inhibitory decrease it
    - - Agonists: chemicals that enhance the action of a neurotransmitter
      - Antagonists: chemicals that counteract a neurotransmitter and prevent a signal from being passed further (many drugs act as agonists and antagonists)
      - Action potential: brief electrical pulse generated by neurotransmitters, that travels along the axon to other neurons
    - - Neurotransmitter stored in vesicles are released in the synaptic gap
      - Neurotransmitter binds to receptors in postsynaptic membrane. If enough of the neurotransmitter binds to the receiving neuron’s receptor site the neuron will fire, transmit message successfully
      - Any unused neurotransmitter is absorbed back to neuron through the process of reuptake, or enzymes will remove it from synaptic cleft
- - - - CAT (Computerized Axial Tomography)
        
        Person lies on a table and enters an apparatus where a moving x-ray source scans the head. Works on the same principle as x-rays but more advanced: more detailed result and 3-D
        
        Because bones/hard tissue absorb x-rays differently to soft tissue, we get a picture of the structure/anatomy of the brain
        
        (+) quick and non-invasive
        
        (+) able to depict soft and hard tissue and blood vessels
        
        (+) people with metals in the bodies can have a CAT
        
        (-) exposure to radiation
        
        Anatomical image of brain density
      - MRI (Magnetic Response Imaging)
        
        Anatomical image of the distribution of certain substances (e.g water, fat)
        
        Person lies on a bed and enters and apparatus with a strong magnetic field. Our bodies emit energy when in magnetic field, which is picked up by the device. Because different molecules have different chemical structure, they emit different energy, and the scanner is able to produce 3D image of our brain.
        
        (+) no radiation
        
        (+) high resolution
        
        (-) excludes people who are claustrophobic, who have metal in their body or who can not stay still
        
        (-) expensive
    - - fMRI (Functional Magnetic Response Imaging)
        
        Functional image of relative blood oxygenation or blood flow
        --> obtains dynamic picture of brain activity
        
        Person enters the apparatus and is required to carry out an activity, altered with periods of inactivity. When a brain area is engaged during the activity, has more oxygenated blood circulating there. This is picked up by the scanner, showing which areas are activated in certain activities.
        
        (+) excellent spatial resolution (able to detect the exact location)
        
        (+) decent temporal resolution (picks up activity within 1 second. For some functions this is more than enough for others not sufficient)
        
        (+) enables us to see brain process, not just structure
        
        (-) a lot of “noise” in obtained data from regular body functions movement
        
        (-) same disadvantages as MRI
        
        (+) easier to carry out
      - PET (Positron Emission Tomography
        
        Functional image of physiological activity for various substances (e.g. glucose, oxygen, and neurotransmitters)
        
        Person needs to be injected with a radioactive “tracer” – a substance that binds to molecules used in the brain. They undertake activities, similar to fMRI.
        
        2.The scanner picks up the radio frequencies emitted by this tracer. Active regions use more blood, so the device can depict which areas are in use.
        
        (+) decent spatial resolution
        
        (+) can be small in size
        
        (-) radioactive substance needs to be injected
        
        (-) very low temporal resolution (30-40 secs)
      - EEG (Electronegelography)
        
        EEG detects electrical signal that provides information about the summed post-synaptic dendritic activity (individual neurons firing impulse is too small to be detected, so EEG picks up large groups of neurons that fire synchronously)
        
        Electrodes attached to the scalp and pick up changes in the electric potential of the scalp areas.
        
        (+) excellent temporal resolution (picks up changes in milliseconds)
        
        (+) low cost, non invasive, silent and mobile
        
        (-) low spatial resolution (not possible to identify the origin location of the signal)
        
        (-) not picking up electrical activity from sub-cortical areas
        
        (-) a lot of “noise” in the data from normal body functions such as heartbeat, blinking etc